[Fiware-ngsi] OMA spec interpretation egarding NGSI10 ONVALUE subscription

[Fermín Galán Márquez]

Hi,

Recently, I have discovered a unambiguity in the OMA spec regarding NGSI10 ONVALUE subscriptions which solution is not clear to me, so I will try to describe it in this email to know what other people involved in NGSI in the project think.

Within the subscribeContextRequest parameters you define a list of entity/attributes (marked in blue in the example below) and a attribute within the ONVALUE condition (marked in red in the example below).

<subscribeContextRequest>
  <entityIdList>
        <entityId type="Room" isPattern="false">
          <id>OfficeRoom</id>
        </entityId>
  </entityIdList>
  <attributeList>
        <attribute>temperature</attribute>
        <attribute>lightstatus</attribute>
        <attribute>pressure</attribute>
  </attributeList>
  <reference>localhost:5000/notify</reference>
  <duration>PT1H</duration>
  <notifyConditions>
        <notifyCondition>
          <type>ONCHANGE</type>
          <condValueList>
                <condValue>temperature</condValue>
          </condValueList>
        </notifyCondition>
  </notifyConditions>
  <throttling></throttling>
</subscribeContextRequest>

My interpretation is that the condValue acts as trigger but what is included in the notifyContext message are the entity/attributes included in the lists under subscribeContextRequest. So, in this case, if temperature changes, then temperature, lighstatus and pressure are notified (although lightstatus and pressure have not changed). In fact, I could even have subscriptions in which the triggering attribute is not part of the attributes being included in the notifyContext message, e.g.

  ...
  <attributeList>
        <attribute>lightstatus</attribute>
        <attribute>pressure</attribute>
  </attributeList>
  ...
          <condValueList>
                <condValue>temperature</condValue>
          </condValueList>
  ...

What do you think?

Best regards,

------
Fermín

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